[0001] The present invention relates to a method and composition for controlling the formation
and deposition of scale forming salts, particularly calcium carbonate, calcium phosphate,
and calcium sulfate, in aqueous mediums. The compositions and methods of the present
invention also act as dispersants for suspended particulate matter, such as clay and
iron oxides.
[0002] Although the invention has general applicability to any given system where the formation
and deposition of calcium carbonate, calcium phosphate and/or calcium sulfate is a
potential problem, or where other problems due to deposition of suspended matter such
as iron oxide and clay, are encountered, the invention will be discussed in detail
as it concerns cooling water and boiling water systems.
[0003] The term "cooling water" is applied whenever water is circulated through equipment
to absorb and carry away heat. This definition includes air conditioning systems,
engine jacket systems, refrigeration systems as well as the multitude of industrial
heat exchange operations, such as found in oil refineries, chemical plants, steel
mills, etc.
[0004] The once-through cooling system, as the name implies, is one in which the water is
passed through the heat exchange equipment and the cooling water is then discharged
to waste. Usually, a once-through system is employed only where water at suitably
low temperature is readily available in large volume and at low cost. The normal source
of once-through cooling water is from wells, rivers and lakes where the cost involved
is that of pumping only. In a once-through system, no evaporation takes place and
consequently the water does not concentrate. Circulating water characteristics are
the same as the makeup-water.
[0005] The use of a recirculating system, in which a cooling tower, spray pond, evaporative
condenser and the like serve to dissipate heat, permits great economy in makeup water
requirements. With dwindling supplies of fresh cold water available for industries'
cooling requirements, increased use must be made of recirculating systems in which
the cooling water is used over and over again.
[0006] After passage of the circulating water through the heat exchange equipment, the water
is cooled when passing over the cooling tower. This cooling effect is produced by
evaporation of a portion of the circulating water in passing over the tower. By virtue
of the evaporation which takes place in cooling, the dissolved solids and suspended
solids in the water become concentrated.
[0007] The circulating water becomes more concentrated than the makeup water due to this
evaporation loss. Cycles of concentration is the term employed to indicate the degree
of concentration of the circulating water as compared with the makeup. For example,
two cycles of concentration indicates the circulating water is twice the concentration
of the makeup water.
[0008] Deposits in lines, heat exchange equipment, etc., may originate from several causes.
For example, the precipitation of calcium sulfate and calcium phosphate will form
scale. In addition, solids foulant particles may enter the system. Through collisions
with neighboring solids particles, these foul ants may agglomerate to a point where
they either foul a heat transfer surface or begin to accumulate in lower flow areas
of the system. On the other hand, corrosion is the electrochemical reaction of a metal
with its environment. It is a destructive reaction and, simply stated, is the reversion
of refined metals to their natural state. For example, iron ore is iron oxide. Iron
ore is refined into steel. When steel corrodes, it also forms iron oxide.
[0009] In speaking of deposits which form in cooling water systems, it is important to bear
in mind the mechanism causing the deposit, otherwise confusion may result. In general,
the term "scale" applies to deposits which result from crystallization or precipitation
of salts from solution. Wasting away of a metal is the result of corrosion. The agglomeration
of suspended solids particles also results in deposit formation. While a deposit re-
sults in all of these cases, the mechanisms of formation are different and different
corrective methods are required to prevent each type of deposit.
[0010] Some of the factors which affect scale formation are temperature, rate of heat transfer,
the calcium, sulfate, magnesium, - silica, phosphate, alkalinity, dissolved solids
and pH of the water.
[0011] In the past in order to minimize the formation of the scale forming salts, cooling
water systems were operated at pH's where the solubility of the "hardness" or "scale
forming" ions was the greatest. Because the pH's of the systems were acidic, corrosion
inhibitors together with dispersants were the normal treatment. Corrosion inhibition
in most instances required chromate treatment. With the advent of tight control regarding
toxic pollutant discharge, operating parameters of cooling water systems had to be
changed in an attempt to utilize non-chromate treatment. The development of high pH
and/or non-chromate corrosion programs over the past few years has concurrently enhanced
the potential for heat exchange fouling due to chemical precipitation. Presently,
most non-chromate treatments include phosphate and/or phosphonic acid compounds, such
as the alkali metal polyphosphates, organo- phosphates, e.g.., phosphate esters, etc.,
amino-trimethylenephosphonic acid, hydroxy ethylidene diphosphonic acid, and water
soluble salts thereof. However, the reversion of the polyphosphates and the organic
phosphates plus the use of alkaline operating conditions leads to the formation and
deposition of the highly insoluble calcium phosphate. Also since there may be phosphate
in the makeup water supply, for example, tertiary sewage treatment effluent for makeup
water, calcium phosphate scaling has become one of the major problems encountered.
Of course, the formation of calcium sulfate in cooling water systems also results
in a scale formation problem. Calcium sulfate is often associated with the use of
sulfuric acid for pH control, especially in connection with sidestream softening,
and with the greater calcium concentrations associated with higher cycles of concentration.
[0012] Another principal scale-forming material encountered in cooling water systems is
calcium carbonate formed by the decomposition of calcium bicarbonate. This compound
has an inverse solubility curve (i.e., the solubility decreases as the system temperature
increases), and its solubility is lower than most of the other potential scale imparting
moieties that may be present in cooling systems. Calcium carbonate is-soluble in acidic
solutions, but since most cooling systems are operated at alkaline conditions to retard
corrosion, calcium carbonate scaling remains a problem.
[0013] Although steam generating systems are somewhat different from cooling water systems,
they share a common problem in regard to deposit formation.
[0014] As detailed in the Betz Handbook of Industrial Water Conditioning, 8th Edition, 1980,
Betz Laboratories, Inc., Trevose, PA, Pages 85-96, the formation of scale and sludge
deposits on boiler heating surfaces is a serious problem encountered in steam generation.
Although current industrial steam producing systems make use of sophisticated external
treatments of the boiler feedwater, e.g., .coagulation, filtration, softening of water
prior to its feed into the boiler system, those operations-are only moderately effective.
In all cases, external treatment does not in itself provide adequate treatment since
muds, sludge, silts and hardness-imparting ions escape the treatment, and eventually
are introduced into the steam generating system. The problems which result from their
introduction into the steam generating system are apparent. Since the deposit forming
materials are present, they have a tendency to accumulate upon concentration of the
water and to settle at points in the system where there is low flow, thus restricting
water circulation. The baking of mud and/or sludge on tubes and sheets will result
in overheating and failure, thereby requiring downtime for repair or replacement of
the structural parts. In addition, mud, sludge and silts may become incorporated in
scale deposits adding to their volume and heat insulating effect.
[0015] Accordingly, internal treatments have been necessary to maintain the mud and silts
in a suspended state. These internal treatments have been generally referred to in
the industry as sludge conditioning agents.
[0016] In addition to the problems caused by mud, sludge- or silts, the industry has also
had to contend with boiler scale. Although external treatment is utilized specifically
in an attempt to remove calcium and magnesium from the feedwater, scale formation
due to residual hardness, i.e., calcium and magnesium salts, is always experienced.
Accordingly, internal treatment, i.e., treatment of the water fed to the system, is
necessary to prevent, reduce and/or retard formation of the scale imparting compounds
and their deposition. The carbonates of magnesium and calcium are not the only problem
compounds as regards scale, but also waters having high contents of phosphate, sulfate
or silicate ions either occurring naturally or added for other purposes cause problems
since calcium and magnesium, and any iron or copper present, react with each and deposit
as boiler scale. As is obvious, the deposition of scale on the structural parts of
a steam generating system causes poorer cir- culation and lower heat transfer capacity,
resulting accordingly in an overall loss in efficiency.
[0017] Although the foregoing is directed for the most part to cooling water systems and
boiler water systems, or more specifically steam generating systems, the same problems
occur in scrubber systems and the like. Any aqueous system having calcium and magnesium
cations and the exemplified anions, particularly the phosphate and sulfate anions,
will experience the formation and deposition of scaling salts.
[0018] Many and different type materials have been used for the treatment of water systems.
Of the yast number may be mentioned alginates, lignins, lignosulfonates, tannins,
carboxymethyl cellulose materials, and synthetic polymers such as polyacrylates and
polymethacrylates. For instance, in U.S. Patent 4,029,577 (God- lewski et al), of
common assignment herewith, certain acrylic acid/ hydroxylated lower alkyl acrylate
copolymers are disclosed as being effective in controlling the formation and deposition
of scale and/ or suspended solid matter which otherwise would occur in aqueous mediums
containing scale imparting ions and dispersed particles.. In U.S. Patent 3,663,448
(Ralston), the formation of solid scale-forming salts in aqueous solution is inhibited
by adding to the solution small amounts of certain amino phosphonate compounds, together
with a water soluble polymer having a molecular weight from about 500 to about 12,000
selected from the group consisting of polyacrylic acid, copolymers of acrylic acid
and up to 50% acrylamide and polyacrylamide in which at least 50% of the amide groups
are hydrolyzed.
[0019] U. S. Patent 4,209,398 (Ii et al) discloses yet another water treating process wherein
a polymer having a structural unit derived from a monomer having an ethylenically
unsaturated bond and having one or more COOH radicals is combined with inorganic phosphates,
phosphonic acids, organic phosphonic acid esters, or polyvalent metal salts, to prevent
scale formation and corrosion.
[0020] U. S. Patents 2,7-23,956 (Johnson); and 3,549,538 (Jacklin); also disclose varied
approaches in the water treatment area. For instance, the '956 Johnson patent discloses
a boiler scale treatment which comprises copolymers of maleic anhydride and other
polymeriza- able mono-ethylenic compounds such as methyl vinyl ether, ethyl vinyl
ether, styrene, alpha-methyl styrene, vinyl acetate, methyl methacrylate, isopentene,
amylene, diisobutylene, isoheptene, nonene, dipentene, ethyl cinnamate or abietic
acid.
[0021] In the '538 Jacklin patent, disclosed are scale inhibition compositions and methods
comprising a nitrilo phosphonate or nitrilo carboxylate compound, such as, nitrilotriacetic
acid or nitrilo- methylene phosphonic acid, and a water soluble sulfoxy free polar
addition polymer having a molecular weight of at least 1,000. Preferred classes of
the water soluble sulfoxy-free polar addition polymers comprise maleic anhydride-styrene
copolymers and acrylic acid homo and copolymers.
[0022] Despite the efforts of the prior art, the water treatment industry is constantly
searching for means for inhibiting scale formation and/or for dispersing solids particulate
matter, efficiently and in a cost effective manner.
General Description of The Invention
[0023] The present inventors have discovered that acrylic acid/ lower alkyl hydroxy acrylate
copolymers (I) in combination with a water soluble polymeric material (II) are particularly
effective in: 1) inhibiting the formation of scale forming salts, including calcium
sulfate, calcium carbonate, and calcium phosphate, and 2) dis- persing solids particulate
matter. The polymeric material (II) may be represented by the formula:
wherein a or b may be zero or a positive integer, with the proviso that a + b > 1;
and wherein d is H or HS0
3. It is to be noted that water soluble salts of the compounds represented by the above
formula are also efficacious. Also, with respect to the polymaleic anhydride monomer
(monomer b), this may hydrolyse to acid form when admitted to the aqueous system to
be treated. It should thus be noted that all such hydrolysed acid forms are within
the scope of the present invention.
[0024] The specific acrylic acid/lower alkyl hydroxy acrylate copolymers (I) utilized in
accordance with the present invention are disclosed in U. S. Patent 4,029,577 (Godlewski
et a1). The entire disclosure of this patent is accordingly incorporated by reference.
[0025] As to the polymers (II) represented by the above Formula, which are-to be utilized
in the combined treatment, sulfonated styrene/maleic anhydride copolymers, styrene/maleic
anhydride copolymers, maleic anhydride homopolymers, and sulfonated styrene homopolymers
are preferred.
[0026] Specifically, the sulfonated styrene/maleic anhydride copolymers which may be used
are represented by the formula:
Preferably, the sulfonated styrene/maleic anhydride copolymers comprise a mole ratio
a:b of from about 2:1 to about 4:1 and preferably about 2:1 to about 3:1, and possess
a molecular weight of from 500 to 100,000. The specific molecular weight is not thought
to be critical, as long as the resulting polymer is water soluble. One preferred polymer
encompassed by Formula II above is sold by the National Starch Company, under the
trademark "Versa-TL-3". This copolymer has a molar ratio a:b of 3:1 and a molecular
weight of about 1500.
[0027] As to the styrene/maleic anhydride copolymers which may be effectively used as part
of the combined treatment, those encompassed by the following formula are exemplary
Copolymers within the scope of Formula III which are thought to be useful for present
purposes include those wherein the molar ratio a:b is between 1:1 and 3:1. The molecular
weight of a Formula III polymer suitable for the present purpose is thought to be
between about 500 to about 50,000. One preferred styrene/mateic anhydride copolymer
within the ambit of Formula III is sold by Arco Chemical under the trademark "SMA
1000". This.particular copolymer has a molar ratio a:b of 1:1 and the molecular weight
thereof is 1,600.
[0028] Turning to the sulfonated styrene homopolymer which may successfully be employed
in combination with the acrylic acid/lower alkyl hydroxy acrylate copolymer (I) in
the particular system to be treated, those within the scope of Formula IV (following)
are thought useful.
Water soluble polymers covered by Formula IV, having a molecular weight of between
about 1,000 to 100,000 are thought to be efficacious. One such sulfonated polystyrene
homopolymer is sold by National Starch Company under the trademark "Versa TL-70."
This particular polymer has a molecular weight of about 70,000.
[0029] The water soluble polymaleic anhydride polymer which may be used as part of the combined
treatment is represented by the formula
The polymaleic anhydride polymer useful for the present purposes will have a molecular
weight of between about 500 and 5,000. One such polymer is sold by Ciba-Geigy under
the trademark "Beiclene 200." This particular polymer has a molecular weight of between
about 800-1000.
[0030] The polymers (I) which are to be utilized in conjunction with the polymeric component
(II) in the combined treatment are those containing essentially moieties (a) derived
from an acrylic acid compound, i.e.,
where R is hydrogen or a lower alkyl of from 1 to 3 carbon atoms and R
1 = OH, 0M, NH
2, where M is a water soluble cation, e.g., NH
4, alkali metal (K, and Na), etc.; and (b) moieties of an hydroxylated lower alkyl
(C = 2-6) acrylate as represented for example by the formula
where R is H, or CH
3 and R
2 is a lower alkyl having from about 2 to 6 carbon atoms (the 0H moiety may be attached
to any of the C atoms in the alkyl group).
[0031] These polymers most advantageously have a mole ratio of moieties derived from an
acrylic acid compound (Formula VI) to hydroxy alkyl acrylate derived moieties of from
about 34:1 to about 1:4, and preferably 11:1 to 1:2, and possess a molecular weight
of from 500 to 1,000,000 and preferably 1,000 to 500,000. The only criteria that is
of importance that applies to the molar ratios of the described monomers in the copolymer,
is that it is desirable to have a copolymer which is soluble in water. It should be
noted that as the proportion of hydroxylated alkyl acrylate moieties increase, the
solubility of the copolymer decreases.
[0032] The polymers (I) utilized in accordance with the invention can be prepared by vinyl
addition polymerization or by treatment of an acrylic acid or salt polymer. More specifically,
acrylic acid or derivates thereof or their water soluble salts, e.g., sodium, potassium,
ammonium, etc. can be copolymerized with the hydroxy alkyl acrylate under standard
copolymerization conditions utilizing free radicals such as benzoyl peroxide, azo
bisisobutyronitrile or redox initiators such as ferrous sulfate and ammonium persulfate.
The molecular weights of the resulting copolymer can be controlled utilizing standard
chain control agents such as secondary alcohols tisopropanol), mercaptans, halocarbons,
etc. Copolymers which may be utilized in accordance with the present invention are
commercially, available from National Starch Company. One preferred copolymer is sold
by National Starch under the trademark "Natrol 42". This particular copolymer is an
acrylic acid/2-hydroxypropyl acrylate copolymer having an acrylic acid: 2-hydroxypropyl
acrylate molar ratio of 3:1 and a molecular weight of about 6000.
[0033] The hydroxyalkyl acrylate can be prepared by-the addition reaction between the acrylic
acid or its derivatives or water soluble salts and the oxide of the alkyl derivative
desired. For example, the preferred monomer of the present invention is the propyl
derivative. Accordingly, to obtain the hydroxylated monomer, acrylic acid is reacted
with propylene oxide to provide the hydroxy propylacrylate monomer constituent of
the copolymer utilized in accordance with the present invention.
[0034] The polymers of the present invention may also be prepared by reacting the .polyacrylic
acid or derivatives thereof with an appropriate amount of an alkylene oxide having
from 2 to 6 carbon atoms such as ethylene oxide, propylene oxide and the like. The
reaction takes place at the COOH or COM group of the moieties to provide the hydroxylated
alkyl acrylate moiety.
[0035] The preferred copolymer prepared either by copolymerization or by reaction of polyacrylic
acid or acrylate with the propylene oxide would be composed of units or moieties having
the structural formulas
where M is as earlier defined and wherein the molar ratio of x to y is preferably
11:1 to 1:2. The copolymer preferably has a molecular weight of from 1,000 to 500,000.
[0036] The operable molar ratio of polymeric material I to poly- meric material II, in accordance
with the invention, is from about 10:1 to 1:10. The preferred molar ratio of polymer
I:polymer II is about 1:1 to 3:1.
[0037] The combined treatment (polymer I and polymer II) should be added to the desired
aqueous system in an amount effective for the purpose, taking into consideration the
respect of concentrations in the water of the potential scale and deposit forming
species, the pH of the water and the chemical and physical properties of the combined
treatment. The criteria for proper treatment of any aqueous system would be apparent
to the worker in the art of water treatment. For the most part, the combined treatment
will be effective when utilized at levels of from about 0.1 to 500 parts per million
of water. Based upon experimental data, the preferred polymeric material II is polymaleic
anhydride. The preferred combined treat- ment comprises administering to an aqueous
medium from about 2-20 parts of acrylic acid/2 hydroxypropylacrylate-polymaleic anhydride
(molar ratio of the acrylate polymer:polymaleic anhydride 3:1) per one million parts
of the aqueous medium to be treated.
[0038] The invention will now be further described with reference to a number of specific
examples which are to be regarded solely as illustrative, and not as restricting the
scope of invention...
[0039] One method of evaluating deposit control activity of a material consists of measuring
its ability to prevent bulk phase precipitation of the salt at conditions for which
the salt would usually precipitate. It is additionally important to recognize that
the material being evaluated is tested at "substoichiometric" concentrations. That
is, typical molar ratios of precipitating cation to the material being evaluated are
on the order of 20:1 and much. greater. Consequently, stoichiometric sequestration
is not the route through which bulk phase precipitation is prevented. The well known
phenomenon is also called "threshold" treatment and is widely practiced in water treatment
technology for the prevention of scale (salt) deposits from forming on various surfaces.
In the results that follow calcium. phosphate, calcium carbonate, and calcium sulfate
salts commonly found in industrial water systems under various conditions have been
selected as precipitants. The combined treatment of the present invention has been
evaluated for its ability to prevent precipitation (i.e., inhibit drystallization)
of these salts. The results are expressed as "percent inhibition", positive values
indicate the stated percentage of the precipitate was prevented from being formed.
Except as where noted to the contrary, the following conditions, solutions, and testing
procedure were utilized to perform the calcium carbonate, calcium phosphate and calcium
sulfate inhibition tests, the results of which are reported herein below in the following
Tables.
CALCIUM PHOSPHATE INHIBITION PROCEDURE
[0040]
Procedure Procedure
1) To about 1800-ml DIH20 in a 2 Titer volumetric flask, add 20 ml of CaCl2.2H20 solution followed by 2 drops of conc. HC1.
2) Add 40 ml of Na2HPO4 solution.
3) Bring volume to. 2 liters with DI water.
4) Place 100 ml aliquots of solution in 4 oz glass bottles.
5) Add treatment.
6) Adjust pH as desired.
7) Place in 70°C water bath and equilibrate for 17 hours.
8) Remove samples and filter while hot through 0.2 u filters.
9) Cool to room temperature and take Absorbance measurements using leitz photometer
(640 nm). Preparation for Leitz
a. 5 ml s filtrate.
b. 10 mls Molybdate Reagent
c. 1 dipper Stannous Reagent
d. Swirl 1 minute, pour into Leitz cuvette; wait 1 minute before reading.
10) Using current calibration curve (Absorbance vs ppm PO4-3) find ppm P04-3 of each sample. Calculation
CALCIUM SULFATE INHIBITION PROCEDURE
[0041]
Procedure
[0042]
1) Add 50 ml of 10-1 CaCl2·2H20 pre-adjusted to pH 7.0 to a 4 oz. bottle.
2) Add treatment.
3) Add 50 ml of 10-1 Na2S04 pre-adjusted to pH 7.0.
4) Heat samples for 24 hours in a 50°C water bath.
5) Cool for 30 minutes, at least.
6) Filter 5 ml through 0.45 u filters.
7) Add NaOH to pH 12.0 and dilute to 50 ml with DI H20.
8) Add Ca+2 indicator (1 level).
9) Titrate to purple-violet endpoint with EDTA.
Calculation
[0043] Calcium Carbonate Inhibition
PROCEDURE
[0044]
1) Add 50 ml CaCl2·2H20 pre-adjusted to pH 9.0
2) Add treatment
3) Add 50 ml Na2C03 pre-adjusted to pH 9.0
4) Heat 5 hours at 70°C water bath. Remove and cool to room temperature.
5) Filter 5 mls through 0.2u filters.
6) Adjust samples to pH <1.0 with conc. HC1 ( lg Conc. HC1)
7) Allow to stand at least 15 minutes.
8) Dilute to 50 mls with DI H20.
9) Bring pH to 12.0 with NaOH.
10) Add Ca+2 indicator (1 nevel).
11) Titrate with EDTA to purple-violet endpoint.
Calculation
[0046] In Table II, it can clearly be seen that the combination of AA/HPA (Polymer I) and
SS/MA (Polymer II) provides deposit control activity that is greater· than expected
from the activity of the individual·materials. Although the combined treatment of
AA/HPA and SS/MA is especially efficacious in inhibiting calcium phosphate formation,
Table I indicates that this combined treatment also serves as an inhibiting treatment
for calcium carbonate and calcium sulfate salts as well.
[0047] Here, the combined AA/HPA + SMA treatment is shown to be exceptionally effective
in controlling CaSO
4 deposit formation. However, the combined treatment, at certain dosage levels and
in certain molar combinations of the individual components, is also effective in inhibiting
and controlling calcium carbonate and calcium phosphate scale accumulation.
[0048] In Table IV, it is clearly demonstrated that the combination of AA/HPA with SMA provides
deposit control activity, with respect to CaS0
4 formation, which is greater than the sum of the inhibition of the component materials.
[0049] From Table VI, it is clearly shown that the inhibition resulting from the combined
AA/HPA-SPS treatment, in calcium phosphate inhibition, is greater than the sum of
the component materials. Table V indicates that this particular combined treatment
is quite effective in calcium phosphate, calcium carbonate and calcium sul- . fate
inhibition.
[0050] Table VII indicates that the combined AA/HPA and PMA treatment is effective as an
inhibitor of calcium carbonate, calcium sulfate, and calcium phosphate salt formation.
It is especially noteworthy that in the 1:1, 1:3, and 3:1 molar ratio (AA/HPA:PMA)
range, the combined treatment is highly efficacious. For instance, within these molar
ranges, a combined treatment of from around 10-20 ppm, inmost instances, shows an
extremely high level of inhibition (about 80% and greater). Accordingly, the AA/HPA-PMA
treatment is preferred.
[0051] Table VIII clearly illustrates that the calcium carbonate inhibition provided by
the combined AA/HPA - PMA treatment is greater than the sum of the component materials.
Similar results are shown in the following Tables IX and X, which respectively are
concerned with additional calcium sulfate and calcium phosphate inhibition tests.
[0052] In order to demonstrate the effectiveness of the combined treatment composition and
method in dispersing suspended particulate matter, the following procedures using
Fe
2O
3 and clay, separately, as suspended solids, were undertaken. The results appear in
the following tables. In the results, it is noted that increasing Δ %T values indicate
better treatment as more particles remain suspended in the aqueous medium.
CLAY DISPERSION (KAOLIN) PROCEDURE
[0053]
Procedure
[0054]
1) Prepare a suspension of 0.1% Hydrite UF in DIH2O.
2) Adjust hardness to 200 ppm Ca+2 as CaCO3-using CaCl2·2H2O sot ution - 8 ml/1000. ml of Hydrite solution.
3) Using overhead mixer, mix suspension 1/2 hour at 1000 rpms.
4) Remoie solution to magnetic stirrer and adjust. to pH 7.5 (about 20 minutes to
stabilize pH).
5) Return solution to overhead mixer.
6) Take 90 ml aliquots of suspension and place 4 oz. glass bottle.
7) Add treatment and DI water to bring total volume to 100 ml.
8) CaD bottle, invert several times and place on reciprocating shaker at a moderate
speed of about 40 spm for 1/2 hour.
9) Place on vibration-proof surface and allow to stand 18 hours.
10) Without disturbing settled phase, pipet the top 40 mls. off the sample. Place
in a cell and read %T (at 415 nm).
Calculation
[0055]
[0056] Fe
2O
3 DISPERSION PROCEDURE
Procedure
[0057]
1) Prepare a suspension of 0.1% Fe2O3 in DIH2O.
2) Adjust hardness to 200 ppm Ca+2 as CaC03 using CaCl2·2N2O solution - 8 ml/1000 ml of Fe203 sotution.
3) Using overhead mixer, mix suspension 1/2 hour at 1000 rpms.
4) Remove solution to magnetic stirrer and adjust to pH 7.5 (about 20 minutes to stabilize
pH).
5) Return solution to overhead mixer.
6) Take 90 ml aliquots of suspension and place 4 oz. glass bottle.
7) Add treatment and DI water to bring total volume to 100 ml.
8) Cap bottle, invert several times and place on reciprocating shaker at a moderate
speed of about 40 spm for 1/2 hour.
9) Place on vibration-proof surface and allow to stand 18 hours.
10) Without disturbing settled phase, pipet the top 40 mls off the sample. Place in
a cell and read %T (at 415 nm)
Calculation
[0058]
[0059] Here, it can be seen that the combined treatment of AA/ HPA - SSMA is also effective
as a dispersant for clay and iron oxide particles.
[0060] In Table XII it is demonstrated that the combined treatment of AA/HPA - SMA acts
as an effective dispersant of iron oxide and clay.
[0061] Table XIV clearly demonstrates that the dispersant activity of the combined AA/HPA
- SPS is greater than the sum of the transmittance values of the component materials.
[0062] Once again, it is demonstrated in Table XV that the combined treatment of AA/HPA
- SPS is synergistic in that the clay transmittance values of the combined treatment
are greater than the sum of the individual component transmittance values.
[0063]
[0064] Here, it can be seen that at a 10 ppm treatment level in both the 1:1 and 3:1 (molar
ratio AA/HPA-PMA) range, the combined treatment is especially efficacious in iron
oxide dispersion capabilities.
[0065] While we have shown and described herein certain embodiments of the present invention,
it is intended that there be covered as well any change o
- modification therein which may be made without departing from the spirit and scope
of the invention as defined in the appended claims.
1..Composition for controlling the deposition of scale imparting precipitates on the
structural parts of a system exposed to an aqueous medium containing scale imparting
precipitates under deposit forming conditions, said composition also being adapted
for dispersing solids particulate matter, characterized in that said composition comprises
an effective amount for the purpose of a water soluble polymer (I) comprising moieties
(a) derived from an acrylic acid or water soluble salt thereof, and moieties (b)'of
an hydroxylated lower alkyl acrylate, wherein the moieties of the polymer have the
following formula
wherein R is hydrogen or a lower alkyl of from about 1 to 3 carbon atoms, R
1 is OH, OM, or NH
2 where_M is a water soluble cation, R
2 is a lower alkyl group of from about 2-6 carbon atoms and the molar ratio of x:y
is about 34:1 to 1:4; and an effective amount for the purpose of a water soluble polymer.
(II) or water soluble salt or hydrolgsate acid form thereof said polymer (II). having
the formula:
wherein a or b may be zero or a positive integer, with the proviso that (a + b) must
be >1, d = H or HSO
3.
2. Composition as claimed in claim 1, characterized in that said scale imparting precipitates
are selected from the group consisting of calcium carbonate, calcium phosphate and
calcium sulphate and said solids particulate matter is selected from the group consisting
of iron oxide, clay and mixtures thereof.
3. Composition as claimed in claim 1 or 2, charac- terized in that said polymer (II)
is a sulfonated styrene/ maleic anhydride copolymer having the formula
4. Composition as claimed in claim 3, characterized in that the molar ratio of a:b
is about 3:1.
5. Composition as claimed in claim 3 or 4, characterized in that the molecular weight
of said sulfonated styrene/maleic anhydride copolymer is about 1500.
6. Composition as claimed in claim 1, characterized in that said polymer (II) is a
sulfonated styrene polymer having the formula
7. Composition as claimed in claim 6, characterized in that said sulfonated styrene
polymer has a molecular weight of about 70,000.
8. Composition as claimed in claim 1, characterized in that said polymer (II) is a
styrene/maleic anhydride polymer having the formula
9. Composition as claimed in claim 8, characterized in that the molar ratio of a:b
is about 1:1.
10. Composition as defined in claim 8 or 9, characterized in that said styrene/maleic
anhydride polymer has a molecular weight of about 1600.
11. Composition as claimed in claim 1, characterized in that said polymer (II) is
a polymaleic anhydride polymer having the formula
12. Composition as claimed in claim 11, characterized in that the molecular weight
of said polymaleic anhydride polymer is about 800-1000.
.13. Composition as claimed in any one of the preceding claims, characterized in that
said polymer (I) comprises acrylic acid/2-hydroxypropyl acrylate copolymer, wherein
the molar ratio of acrylic acid to 2 hydroxypropyl acrylate copolymer is about 3:1
and wherein the molecular weight of said acrylic acid/2 hydroxypropyl acrylate copolymer
is about 6,000.
14. Method of treating an aqueous medium so as to
(i) control the deposition of scale imparting precipitates on the structural parts
of a system exposed to an aqueous medium containing scale imparting precipitates under
deposit forming conditions, and/or
(ii) disperse and maintaining dispersed particulate- matter in such a system having
an aqueous medium which contains particulate matter;
which method is characterized by adding to said aqueous medium an effective amount
for the purpose of a water soluble polymer (I) as defined in claim 1 or 13; and also
adding to said aqueous medium and effective amount for the purpose of a water soluble
polymer (II) as defied in any one of claims 1 to 12, or water soluble salt or hydrolysate
acid form thereof.
15. Method as claimed in claim 14, characterized in that. said scale imparting precipitates
are selected from the group consisting of calcium carbonate, calcium phosphate and
calcium sulphate and said solids particulate . matter is selected from the group consisting
of clay, iron . oxide and mixtures thereof.
16. Method as claimed in claim 14 or 15, characterized in that the molar ratio of
polymer (I) to polymer (II) is about 10:1 to 1:10, and wherein said polymer (I) and
polymer (II) are added to said aqueous medium in an amount of about 0.1-500 parts
polymer (I) and (II) per million parts of said aqueous medium.
17. Method as claimed in claim 14 or 15, characterized in that said system is a steam
generating system.
18. Method as claimed in claim 14 or 15, characterized in that said system is a cooling
water system.
19. Method as claimed in any one of claims 14 to 18, characterized in that said polymer
(I) has a molecular weight of from about 500 to 1,000,000.
20. Method as claimed in any one of claims 14 to 19, characterized in that said polymer
(I) comprises a copolymer of acrylic acid or a water soluble salt thereof and 2-hydroxypropyl
acrylate or hydroxyethylacrylate.
21. Aqueous medium characterized by having been treated by a composition as claimed
in any one of claims 1 to 13, or a method as claimed in any one of claims 14 to 20.